A girl that is the lowest human being in the world and that would screw you over in a heart beat even if you have always been loyal and there for her. Also known as "BFK"

(Friend) Did you hear what that girl did to my brother?
(Friend 2) No what happened?
(Friend) After his house burnt down she cheated on him and gave away his stuff. Not only was he homeless, he litelly had no possesions.
(Friend 2)Wow that girl is a real bitch face killer!
(Friend) Yep, she is a BFK alright!